1. Field of the Invention
The present invention relates to a supporting pin for supporting and delivering a substrate such as a glass substrate or a semiconductor wafer.
2. Description of the Related Art
In order to form a resist film or a color filter film on a glass substrate in a conventional method for manufacturing a liquid crystal display (LCD), a material for the film (coating liquid) is applied onto a surface of the glass substrate, and the coating liquid is heated within a heat treatment apparatus so as to form the film. As shown in FIG. 5, a supporting pin 102 is provided so as to be elevated or lowered in a penetrating hole 101 formed in the hot plate 100 in the vertical direction. In order to deliver the glass substrate onto the hot plate of the heat treatment apparatus, the supporting pin 102 is elevated above the upper surface of the hot plate 100, and the glass substrate W is delivered onto the upper end of the supporting pin 102, thereafter the supporting pin 102 is lowered so as to mount the glass substrate W on the hot plate 100.
There has been disclosed a technique for improving the above-described supporting pin in Patent Document 1 and Patent Document 2. Specifically, Patent Document 1 has disclosed a heat treatment apparatus for performing heat treatment in a state where a substrate is mounted on a supporting pin made of polyimide resin. Patent Document 2 has disclosed a heat treatment apparatus in which a supporting pin made of a fibrous material is provided on a base formed on a delivery arm, so that heat stored above the substrate is transferred from the supporting pin while diffused and the trace of the supporting pin left on the substrate is made de minimis compared to the conventional art.
Patent document 1: Japanese Patent Application publication No. 2003-218003
Patent document 2: Japanese Patent Application publication No. 2000-012655
When electricity is applied to the hot plate, the temperature of the hot plate itself becomes too high, which causes thermal expansion of the hot plate. A plurality of penetrating holes for inserting a supporting pin are formed in the hot plate such that the penetrating holes are equally arranged with respect to the whole area of the upper surface of the hot plate. If thermal expansion of the hot plate occurs in this structure, the penetrating holes located in the area other than the central area are moved toward the outside. Consequently, the side surface of the penetrating hole butts against the supporting pin, which causes the supporting pin to be bent and makes it difficult for the supporting pin to be elevated and lowered smoothly. In some cases, the supporting pin cannot be elevated and lowered with respect to the penetrating hole.